In the field of hydrocarbon exploration and production, it is common to use actuator devices and tools to controllably actuate or operate from surface downhole components and tools between first and second operational conditions. A typical application is the setting and/or releasing of a downhole plug or packer during a wellbore operation. Other applications include but are not limited to setting straddles, whipstocks, and/or cement retainers. A wide range of setting tools have been developed or proposed for use with different drive systems, and many have been used in the field with successful results. The majority of setting tools are hydraulically operated, and use hydraulically actuated pistons to drive a setting mechanism, which is often (but not always) configured to force an outer sleeve downwards with respect to an inner rod or mandrel.
Drive systems used to operate setting tools include gas drive systems, pump drive systems, and hydrostatic pressure drive systems. In a gas drive system, a downhole module is used to generate high pressure gas from a pyrotechnic device, a chemical reaction, or a thermal reaction. The high pressure gas drives the actuator pistons of the setting tool, either by directly acting on the actuator pistons, or by driving a piston down to generate a flow of hydraulic fluid to the actuator pistons. Typical pressures generated from pyrotechnic systems of this type are around 62,000 kPa to 90,000 kPa (around 9,000 psi to 13,000 psi), which is sufficient for many downhole setting applications.
An example of a gas drive setting tool is disclosed in U.S. Pat. No. 5,396,951. A preferred embodiment uses a resistance heater to initiate a pyrotechnic chemical reaction and generate a gas pressure which acts on a primary floating piston. The floating piston acts on hydraulic fluid to pressurise a secondary piston, which in turn transfers a force to a setting sleeve. The described setting tool is said to avoid the requirement for primary and secondary igniters, and is said to enable a single drive module to be assembled, sold and shipped.
Pump drive systems use a combination of a motor and a pumps, which may be located downhole or at surface. Downhole pump drive systems have been developed as an alternative to pyrotechnic drive mechanisms such as that disclosed in U.S. Pat. No. 5,396,951. A downhole pump drive system uses electric current from surface or downhole batteries to drive a motor, which in turn drives a high pressure pump. The pump causes hydraulic fluid to flow to the actuator pistons of the setting tool. A surface pump drive system uses a surface motor and pump to cause fluid to be pumped from surface down drill pipe or coiled tubing to the setting tool system where it acts on the actuator pistons.
Limitations to the pressure capabilities of downhole pumps has led to the use of multistage, stacked piston arrangement with downhole pump drive systems in order to increase the available setting force. More recently, WO2014/170640 describes a non-explosive setting tool which uses high pressure downhole pumps to generate a system pressure of up to around 96,500 kPa (about 14,000 psi) in a single-stage actuation system. The setting tool comprises a downhole motor and pump assembly which is used to pump hydraulic fluid from a first chamber to drive a piston arrangement between an unset and a set position. After use, a plug is opened to enable return of hydraulic fluid from the piston chamber back to the first fluid chamber, ready for reuse.
Hydrostatic drive systems comprise a mechanism configured to open a valve and expose a flow system in the setting tool to hydrostatic pressure. The hydrostatic pressure causes wellbore fluids to enter the flow system and actuate the pistons to operate the tool. Depending on the available hydrostatic pressure, hydrostatic drive systems may use stacked piston arrangements to provide the desired setting force.
An alternative mechanism is disclosed in WO 2012/150189, which describes a setting tool with first and second fluid chambers fluidly connected via first and second channels. Fluid is pumped from the first chamber to the second chamber via the flow channels. The volume of the first chamber is adjusted to maintain an ambient pressure condition in the first chamber while a fixed volume of the second chamber becomes pressurised and charges a spring-loaded piston. A trigger releases a sleeve from an inner mandrel and causes relative movement of the sleeve and the mandrel to a setting position. After use, the pressure in the first and second chamber can be equalised by reversing the pumping direction or through an optional additional flow channel which is open in the fully set position of the tool.
U.S. Pat. No. 7,913,770 describes a setting tool with a porous plug that enables an atmospheric chamber to be equalised to wellbore pressure after actuation of the tool.
While the above-described setting tools may be useful in certain applications, many of these systems have significant drawbacks. Firstly, the use of pyrotechnics in gas drive modules and systems requires special permits and particular safety considerations which complicate operation and logistics.
The use of downhole motors and pump modules addresses these safety issues, but the motors and pumps themselves are often relatively expensive and complex, presenting commercial and technical barriers to their widespread use. Surface pumps and hydrostatic systems may be limited in the available input pressure, and may therefore provide insufficient actuation force for some applications (particular those which require higher setting or release forces). In addition, in hydrostatic applications, fluid levels may be uncertain and therefore the available hydrostatic pressure and actuation force may not be reliably known.
Other drawbacks include the specificity of setting tools to a particular category of drive module (or proprietary drive module), and a fixed force output from the actuator device. Furthermore, typically actuator devices are unidirectional; they can only provide a force one direction. These drawbacks limit the operational efficiency of the tools and increase operational inventory.
In addition, many downhole plug systems rely on the shearing of a solid shear stud or shear ring attached to the plug in order to release the setting tool from the plug at the end of the setting sequence. A consequence of these configurations is that in the event of a failure in the setting tool system, which may result from motor burn out, a damaged piston seal or a gas leak, the setting tool can remain permanently attached to the plug which is partially set in the wellbore. This represents a significant operational problem and in some extreme cases may result in the loss of the well. Furthermore, in some cases, such as a burnt out motor-pump drive system, or an insufficient fluid column when relying on hydrostatic pressure, the partial setting force remains ‘trapped’ in the tool. This prevents various contingencies that might otherwise be employed (for example, a mechanical release system) from releasing the setting tool from the plug.